Fermented food, method for producing same, and method for improving survival of bifidobacteria

Abstract

This fermented food, obtained by fermenting a raw material composition comprising bifidobacteria, Lactococcus bacteria, and an iron-containing compound, exhibits excellent bifidobacteria survival.

Description

Fermented food, its manufacturing method, and method for improving the survival rate of bifidobacteria

[0001] The present invention relates to a fermented food, a method for producing a fermented food, and a method for improving the viability of bifidobacteria.This application claims priority based on Japanese Patent Application No. 2023-132859, filed on August 17, 2023, the contents of which are incorporated herein by reference.

[0002] Bifidobacterium bacteria (hereafter referred to as "bifidobacteria") are representative of useful intestinal bacteria (also known as "probiotics") known for their many physiological functions, including protection against pathogenic bacteria, and there is growing demand for foods containing live bifidobacteria. However, bifidobacteria grow poorly in milk-based media and have poor survival rates in acidic environments, making it difficult to maintain bifidobacteria in fermented foods.

[0003] To address this issue, Patent Document 1 proposes a method for improving the survival rate of bifidobacteria in fermented milk by fermenting the milk using bifidobacteria and bacteria belonging to Lactococcus lactis as lactic acid bacteria.

[0004] Japanese Patent No. 4772131

[0005] Higher survival rates of bifidobacteria are preferred, and it is desired to further improve the survival rate of bifidobacteria compared to the method described in Patent Document 1. An object of the present invention is to provide a fermented food product with excellent survival rates of bifidobacteria.

[0006] The present invention has the following aspects. [1] A fermented food comprising bifidobacteria, Lactococcus bacteria, and an iron-containing compound. [2] The fermented food according to [1], wherein the iron content per 100 g of the fermented food is 0.3 mg or more. [3] The fermented food according to [1] or [2], wherein the iron-containing compound contains non-heme iron. [4] The fermented food according to [3], wherein the iron-containing compound contains one or more compounds selected from the group consisting of ferric pyrophosphate, ferrous citrate, and ammonium ferric citrate. [5] The fermented food according to [3], wherein the content of live bifidobacteria per 100 g of the fermented food is 1 x 10 ８cfu or more. [6] The fermented food according to any one of [1] to [5], wherein the bifidobacterium comprises one or more species selected from the group consisting of Bifidobacterium longum and Bifidobacterium breve. [7] The fermented food according to any one of [1] to [6], wherein the Lactococcus bacteria comprise Lactococcus lactis. [8] The fermented food according to any one of [1] to [7], wherein the fermented food is fermented milk. [9] A method for producing a fermented food, comprising a step of fermenting a raw material composition containing bifidobacteria, Lactococcus bacteria, and an iron-containing compound.

[10] A method for improving the viability of bifidobacteria in a fermented product obtained by fermenting a raw material composition containing bifidobacteria, the method comprising fermenting a raw material composition containing bifidobacteria, Lactococcus bacteria, and an iron-containing compound.

[0007] According to the present invention, a fermented food product having excellent survival rates of bifidobacteria can be obtained.

[0008] 1 is a graph showing the measurement results of bifidobacteria after storage in Examples 5 to 7. 2 is a graph showing the measurement results of bifidobacteria after storage in Examples 8 to 10. 3 is a graph showing the measurement results of bifidobacteria after storage in Examples 11 to 14. 4 is a graph showing the measurement results of bifidobacteria after storage in Examples 15 to 19. 5 is a graph showing the measurement results of bifidobacteria after storage in Examples 15, and 20 to 23. 6 is a graph showing the measurement results of bifidobacteria after storage in Examples 24 to 27.

[0009] Fermented foods in this specification refer to foods containing fermented products obtained by fermenting a fermentation substrate with fermenting bacteria. Among fermented foods, fermented milk refers to a paste or liquid product obtained by fermenting milk or milk containing an equivalent or greater amount of non-fat milk solids with fermenting bacteria. Here, "milk" may be milk derived from mammals, such as milk derived from cows, sheep, or goats. Bovine milk (i.e., cow's milk) is preferred. The fermented food of the present invention contains bifidobacteria, Lactococcus bacteria, and an iron-containing compound.

[0010] Bifidobacteria are bacteria belonging to the genus Bifidobacterium. Any known bifidobacteria can be used in fermented foods. For example, Bifidobacterium longum subsp. longum, Bifidobacterium breve, Bifidobacterium longum subsp. infantis, Bifidobacterium bifidum, Bifidobacterium lactis, Bifidobacterium animalis, animalis), and Bifidobacterium adolescentis. Bifidobacterium longum subsp. longum may be abbreviated simply as Bifidobacterium longum. Bifidobacterium longum subsp. infantis may be abbreviated simply as Bifidobacterium infantis. In the present invention, Bifidobacterium longum subsp. longum and Bifidobacterium breve are preferred. Among these, Bifidobacterium longum subsp. longum BB536 (NITE BP-02621, hereinafter also referred to simply as "NITE BP-02621") and Bifidobacterium breve MCC1274 (FERM BP-11175, hereinafter also referred to simply as "FERM BP-11175") are preferred. One type of bifidobacterium may be used, or two or more types may be used in combination.

[0011] The bacterium assigned the accession number NITE BP-02621 was internationally deposited under the Budapest Treaty on January 26, 2018, at the Patent Microorganisms Depositary Center of the National Institute of Technology and Evaluation (Room 122, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture, 292-0818) under the accession number NITE BP-02621. This bacterium is the same bacterium as Bifidobacterium longum subsp. longum BB536. The bacterium, assigned the accession number FERM BP-11175, was internationally deposited under the Budapest Treaty with the Patent Organism Depositary of the National Institute of Advanced Industrial Science and Technology (currently the Patent Organism Depositary of the National Institute of Technology and Evaluation, Room 120, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture, 292-0818) on August 25, 2009. This bacterium is identical to Bifidobacterium breve MCC1274.

[0012] The lactococcus bacteria can be any known lactococcus bacteria used in fermented foods. For example, Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, and Lactococcus plantarum can be mentioned. Note that Lactococcus lactis subsp. lactis may be abbreviated simply as Lactococcus lactis. Furthermore, Lactococcus lactis subsp. cremoris may be abbreviated simply as Lactococcus cremoris. In the present invention, Lactococcus lactis subsp. lactis is preferred. Lactococcus lactis subsp. lactis includes Lactococcus lactis subsp. lactis NITE BP-1204, Lactococcus lactis subsp. lactis NITE BP-1205, Lactococcus lactis subsp. lactis MCC852 (FERM BP-10742), Lactococcus lactis subsp. lactis MCC857 (FERM BP-10757), Lactococcus lactis subsp. lactis MCC859 (FERM BP-10744), and Lactococcus lactis subsp. lactis MCC865 (FERM BP-10745). lactis MCC866 (FERM BP-10745), and Lactococcus lactis subsp. lactis MCC866 (FERM BP-10746). Among these, Lactococcus lactis subsp. lactis NITE BP-1204 (hereinafter also simply referred to as "NITE BP-1204") is preferred.The bacteria assigned the accession number NITE BP-1204 and the bacteria assigned the accession number NITE BP-1205 have been internationally deposited on January 17, 2012, at the Patent Microorganisms Depositary Center of the National Institute of Technology and Evaluation (Room 122, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture, 292-0818) under the Budapest Treaty. The bacteria assigned accession numbers FERM BP-10742, FERM BP-10744, FERM BP-10745, and FERM BP-10746 have been internationally deposited on December 1, 2006, under the Budapest Treaty, with the National Institute of Advanced Industrial Science and Technology (currently the National Institute of Technology and Evaluation (NITE) Patent Organism Depositary, Room 120, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture, 292-0818). The bacterium assigned the accession number FERM BP-10757 was internationally deposited under the Budapest Treaty with the Patent Organism Depositary of the National Institute of Advanced Industrial Science and Technology (currently the Patent Organism Depositary of the National Institute of Technology and Evaluation, Room 120, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture, 292-0818) on January 10, 2007. One species of Lactococcus bacterium may be used, or two or more species may be used in combination.

[0013] In the present invention, it is particularly preferred to use one or both of NITE BP-02621 and FERM BP-11175 as bifidobacteria and NITE BP-1204 as Lactococcus bacteria.

[0014] The iron-containing compound may be any known iron-containing compound that can be added to foods. Iron-containing compounds containing non-heme iron are preferred. Known iron-containing compounds containing non-heme iron can be used. Examples include ferric pyrophosphate, ferrous citrate, and ammonium ferrous citrate. The iron-containing compound containing non-heme iron may be in the form of a suitable salt, for example, ferrous citrate may be sodium ferrous citrate. One type of iron-containing compound may be used, or two or more types may be used in combination.

[0015] The iron content per 100 g of the fermented food is preferably 0.3 mg or more, more preferably 0.6 mg or more, even more preferably 0.9 mg or more, even more preferably 2.5 mg or more, even more preferably 5.0 mg or more, and even more preferably 10.0 mg or more. When the iron content is equal to or greater than the above lower limit, the effect of improving the viability of bifidobacteria is excellent. The upper limit is not particularly limited, but from the viewpoint of flavor, it is preferably 25 mg or less, more preferably 20 mg or less, and even more preferably 15 mg or less.

[0016] In this specification, the iron content is measured by ICP (inductively coupled plasma) spectrometry. The iron content of the fermented food may be calculated based on the iron content and the amount of raw materials used to produce the fermented food.

[0017] The iron content per 100 g of the fermented food may be 0.3 mg to 25 mg, 0.3 mg to 20 mg, 0.3 mg to 15 mg, 0.6 mg to 25 mg, 0.6 mg to 20 mg, 0.6 mg to 15 mg, 0.9 mg to 25 mg, 0.9 mg to 20 mg, 0.9 mg to 15 mg, 2.5 mg to 25 mg, 2.5 mg to 20 mg, 2.5 mg to 15 mg, 5.0 mg to 25 mg, 5.0 mg to 20 mg, 5.0 mg to 15 mg, 10.0 mg to 25 mg, 10.0 mg to 20 mg, or 10.0 mg to 15 mg.

[0018] The content of live bifidobacteria per 100g of fermented food is 1x10 ８ cfu or more is preferred, and 1 x 10 ９ cfu or more is more preferable, and 1 x 10 １０ In this specification, the content of viable bifidobacteria is a value obtained by the measurement method described in the Examples below.

[0019] The content of live bifidobacteria per 100g of fermented food is 1 x 10 ８ cfu or more 1 x 10 １３ less than cfu, 1×10 ８ cfu or more 1 x 10 １２ less than cfu, 1×10 ８ cfu or more 5 x 10１１ less than cfu, 1×10 ９ cfu or more 1 x 10 １３ less than cfu, 1×10 ９ cfu or more 1 x 10 １２ less than cfu, 1×10 ９ cfu or more 5 x 10 １１ less than cfu, 1×10 １０ cfu or more 1 x 10 １３ less than cfu, 1×10 １０ cfu or more 1 x 10 １２ cfu or less, or 1 x 10 １０ cfu or more 5 x 10 １１ It may be less than or equal to cfu.

[0020] Fermented foods contain water. The solid content of the fermented food is preferably 3% by mass to 28% by mass, more preferably 5% by mass to 26% by mass, and even more preferably 8% by mass to 23% by mass. When the fermented food is fermented milk, the non-fat milk solids content is preferably 2.9% by mass to 20% by mass, more preferably 4.9% by mass to 18% by mass, and even more preferably 7.9% by mass to 15% by mass, relative to the total mass of the fermented food.

[0021] In this specification, the solid content is a value calculated by "solid content (unit: mass %) = 100 - moisture (unit: mass %)". The moisture content is a value measured by a normal pressure heating and drying method. Specifically, a sample is dried in an incubator at 99°C for 4 hours, the weight loss is measured, and the moisture content is calculated using the following formula: Moisture (unit: mass %) = (mass of sample before drying (unit: g) - mass of sample after drying (unit: g)) / mass of sample before drying (unit: g) × 100

[0022] The non-fat milk solids content is the value obtained by subtracting the fat (also called milk fat) content from the milk-derived solids (also called milk solids). The fat content is measured by the Roese-Gottlieb method. Specifically, 3 g of sample is placed in a Majornier tube, and 7 ml of water, 1 drop of phenolphthalein, and 2 ml of ammonia water are added and gently shaken. Then, 10 ml of ethanol, 25 ml of ethyl ether, and 25 ml of petroleum ether are added, with the stopper closed and shaken two or three times after each addition. The Majornier tube is centrifuged, and the solvent layer is transferred to a dish, and the solvent is evaporated. This residue is fat. The residue is weighed to determine the fat mass. The ratio of fat mass to 3 g of sample is determined to determine the fat content (unit: mass %).

[0023] Fermented foods include fermented products. When the fermented food is fermented milk, it includes a fermented product obtained by fermenting a raw material composition containing a dairy ingredient with fermenting bacteria. The dairy ingredient can be any known ingredient used in the production of fermented milk. Examples include raw milk, cream, concentrated skim milk, skim milk powder, and milk protein concentrate. A single dairy ingredient may be used, or two or more dairy ingredients may be used in combination. When the fermented food is not fermented milk, it includes a fermented product obtained by fermenting a raw material composition containing a fermentation substrate other than a dairy ingredient with fermenting bacteria. Examples of fermented substrates other than dairy include plant-based milk. Plant-based milk refers to milky foods obtained from plant ingredients. Examples of plant-based milk include soy milk, almond milk, rice milk, coconut milk, and oat milk. A single plant-based milk may be used, or two or more plant-based milks may be used in combination. The raw material composition may further include known ingredients in fermented foods, such as sugars, vegetable fats, stabilizers, flavorings, pH adjusters, fruit juice / pulp, and sweeteners. Examples of stabilizers include agar, gelatin, and pectin. Examples of the sweetener include sucralose. Fermenting bacteria include bifidobacteria and Lactococcus bacteria. Other fermenting bacteria may also be included. Examples of other fermenting bacteria include Streptococcus thermophilus (S. thermophilus) and Lactobacillus bulgaricus (L. bulgaricus). One type of other fermenting bacteria may be used, or two or more types may be used in combination. Known lactic acid bacteria starters may also be used as other fermenting bacteria.

[0024] The pH of the fermented food at 10°C is preferably 3.7 or higher and 5.0 or lower, more preferably 4.0 or higher and 4.7 or lower.

[0025] The content of viable bifidobacteria decreases during storage of a fermented food. As will be shown in the Examples below, the present invention provides a fermented food with excellent viability of bifidobacteria. For example, if the storage period from production to the end of the day following the production date (i.e., day 0) is assumed to be one day, the content of viable bifidobacteria per 100 g of the fermented food will be 1 x 10 ９ The fermented food obtained has a period of 7 days or more, preferably 11 days or more, more preferably 14 days or more, and more preferably 21 days or more, during which the viable Bifidobacterium content per 100 g of the fermented food is maintained at 3.5 x 10 ９ A fermented food can be obtained in which the number of cfu or more is maintained for a period of 7 days or more, preferably 11 days or more, more preferably 14 days or more, and more preferably 21 days or more.

[0026] The content of live bifidobacteria in the fermented food at the start of storage is not particularly limited. For example, the content of live bifidobacteria per 100 g of the fermented food at the start of storage is 1 x 10 １３ cfu or less, and may be 1 x 10 １２ cfu or less, and may be 5 x 10 １１ It may be less than or equal to cfu.

[0027] The fermented food of the present invention may contain optional ingredients as appropriate within the scope of not impairing the effects of the present invention, such as animal or vegetable fats and oils, dietary fiber, emulsifiers, stabilizers, thickeners, sugars, sugar alcohols, polysaccharides, pH adjusters, fatty acid esters, flavorings, fragrances, sweeteners, coloring agents, excipients, etc.

[0028] The fermented food of the present invention can be produced by a method including a fermentation step in which a raw material composition containing bifidobacteria, Lactococcus bacteria, and an iron-containing compound is fermented to obtain a fermented product. The composition of the raw material composition is preferably designed according to the composition of the fermented product to be obtained. The total mass of the raw material composition is the same as the total mass of the fermented product at the end of the fermentation step. In the raw material composition, "iron / bifidobacteria," which represents the ratio of the iron content (unit: mg / 100 g) to the content of live bifidobacteria (unit: cfu / 100 g), is 1.0 x 10 －１２ Above 1.0 x 10 －６ Preferably, the value is 1.0 x 10 or less. －１１ Above 1.0 x 10 －７ Less than 1.0 × 10 is more preferable. －１０ Above 1.0 x 10 －８ The following is even more preferred: In the raw material composition, the "Lactococcus bacteria / Bifidobacteria" ratio, which represents the ratio of the content of Lactococcus bacteria (unit: cfu / 100 g) to the content of live Bifidobacteria (unit: cfu / 100 g), is 1.0 x 10 －２ Preferably, 5.0 x 10 or more and 10 or less. －２ More preferably, 3.0 × 10 －１ It is more preferable that the iron content per 100 g of the fermented food is the same as the iron content per 100 g of the raw material composition. When no iron is added after the fermentation step is completed, the iron content per 100 g of the fermented food is the same as the iron content per 100 g of the raw material composition.

[0029] In the preparation process of the raw material composition, raw materials other than the fermenting bacteria are mixed, preferably homogenized, and then heat sterilized, and the fermenting bacteria are added (also called inoculated) to obtain the raw material composition. The homogenization and heat sterilization can be carried out by conventional methods.

[0030] In the fermentation step, the raw material composition containing the fermenting bacteria is fermented by maintaining it at a predetermined fermentation temperature. The fermentation temperature is, for example, preferably 35°C or higher and 43°C or lower, and more preferably 37°C or higher and 41°C or lower. As the fermentation progresses, the pH of the raw material composition decreases. When a predetermined end point pH is reached, the composition is cooled to obtain a fermented product. The end point pH is, for example, preferably 4.0 or higher and 5.0 or lower, and more preferably 4.2 or higher and 4.8 or lower. The temperature after cooling is, for example, preferably 3°C or higher and 15°C or lower, and more preferably 5°C or higher and 10°C or lower. The fermentation step can be carried out by a known method. The fermented product obtained after the fermentation step may be used as a fermented food as is, or may be further processed to obtain a fermented food.

[0031] The product form of the fermented food is not particularly limited. For example, in the production of fermented milk, a raw material composition is fermented while contained in a product container such as a cup, to obtain static fermented milk. Alternatively, the raw material composition is fermented in a tank or the like, and the resulting fermented product (also called curd) is stirred and crushed and filled into a product container to obtain stirred fermented milk or drink-type fermented milk. In particular, when producing drink-type fermented milk, it is preferable to smooth the fermented product (also called curd). Smoothing refers to a process of crushing the fermented product to make it smooth. Any crushing means known in the production of fermented milk can be used as the crushing means. Specific examples include a homogenizer, a back-pressure valve, a filter, a pump, etc.

[0032] According to the present invention, it is possible to improve the viability of bifidobacteria in a fermented product obtained by fermenting a raw material composition containing live bifidobacteria. As shown in the Examples below, when a raw material composition containing bifidobacteria, Lactococcus bacteria, and an iron-containing compound is fermented, the viability of bifidobacteria in the fermented product obtained by fermentation is improved compared to when the raw material composition contains bifidobacteria but does not contain either or both of Lactococcus bacteria and the iron-containing compound.

[0033] The method for improving the viability of bifidobacteria of the present invention is a method for improving the viability of bifidobacteria in a fermented product obtained by fermenting a raw material composition containing bifidobacteria, and includes a step of fermenting a raw material composition containing bifidobacteria, Lactococcus bacteria, and an iron-containing compound. In the present invention, improving viability means that the decrease in the viable cell count of bifidobacteria during storage of a fermented food is gradual. When fermented foods that have been stored for the same period of time are compared, the fermented food with improved viability has a higher viable cell count of bifidobacteria. For example, if the content of viable bifidobacteria per 100 g of fermented food at the start of storage is 1 x 10 １２ cfu over 1 x 10 １３ cfu or less, and the content of live bifidobacteria per 100 g of fermented food is 1 x 10 ９ The period during which the viable Bifidobacterium content is maintained at 1 x 10 cfu or more per 100 g of the fermented food at the start of storage may be 7 days or more, 11 days or more, 14 days or more, or 21 days or more. １２ cfu over 1 x 10 １３ cfu or less, and the content of live bifidobacteria per 100 g of fermented food is 3.5 x 10 ９ The period during which the viable Bifidobacterium content is maintained at 5×10 cfu or more per 100 g of the fermented food at the start of storage may be 7 days or more, 11 days or more, 14 days or more, or 21 days or more. １１ cfu over 1 x 10 １２ cfu or less, and the content of live bifidobacteria per 100 g of fermented food is 1 x 10 ９ The period during which the viable Bifidobacterium content is maintained at 5×10 cfu or more per 100 g of the fermented food at the start of storage may be 7 days or more, 11 days or more, 14 days or more, or 21 days or more. １１ cfu over 1 x 10 １２ cfu or less, and the content of live bifidobacteria per 100 g of fermented food is 3.5 x 10 ９ The period during which the viable Bifidobacterium content is maintained at 1 x 10 cfu or more per 100 g of the fermented food at the start of storage may be 7 days or more, 11 days or more, 14 days or more, or 21 days or more. １０ cfu or more 5 x 10１１ cfu or less, and the content of live bifidobacteria per 100 g of fermented food is 1 x 10 ９ The period during which the viable Bifidobacterium content is maintained at 1 x 10 cfu or more per 100 g of the fermented food at the start of storage may be 7 days or more, 11 days or more, 14 days or more, or 21 days or more. １０ cfu or more 5 x 10 １１ cfu or less, and the content of live bifidobacteria per 100 g of fermented food is 3.5 x 10 ９ The period during which the number of cfu or more is maintained may be 7 days or more, 11 days or more, 14 days or more, or 21 days or more.

[0034] The present invention has the following aspects: <1> A method for producing fermented milk comprising the steps of heat-sterilizing a mixture containing one or more iron-containing compounds selected from the group consisting of ferric pyrophosphate, ferrous citrate, and ammonium ferric citrate, a milk raw material, and water, and then adding fermentation bacteria containing bifidobacteria and Lactococcus bacteria to obtain a raw material composition, fermenting the raw material composition until the pH reaches 4.2 to 4.8, and then cooling the raw material composition to obtain fermented milk, wherein the raw material composition has a solid content of 8% to 23% by mass and a non-fat milk solid content of 7.9% to 15% by mass, relative to the total mass of the raw material composition, the iron content per 100 g of the raw material composition is 0.3 mg to 15 mg, and the "iron / bifidobacteria" ratio, which represents the ratio of the iron content (unit: mg / 100 g) to the content of live bifidobacteria (unit: cfu / 100 g) in the raw material composition, is 1.0 x 10 －１０ Above 1.0 x 10 －８ or less, and "Lactococcus bacteria / Bifidobacteria", which represents the ratio of the content of Lactococcus bacteria (unit: cfu / 100 g) to the content of live Bifidobacteria (unit: cfu / 100 g), is 3.0 x 10 －１ and the content of live bifidobacteria per 100 g of the fermented milk immediately after cooling is 1 x 10 or more and 1 or less. １０ cfu or more 5 x 10 １１cfu or less. <2> The method for producing fermented milk according to <1> above, wherein the raw material composition contains no iron other than the iron-containing compound, and no iron is added after the fermented milk is obtained by cooling. <3> The method for producing fermented milk according to <1> or <2> above, wherein the bifidobacterium is one or both of Bifidobacterium longum subsp. longum and Bifidobacterium breve, and the Lactococcus bacterium is Lactococcus lactis subsp. lactis. <4> The method for producing fermented milk according to <1> or <2> above, wherein the bifidobacterium is one or both of NITE BP-02621 and FERM BP-11175, and the Lactococcus bacterium is NITE BP-1204. <5> The method for producing fermented milk according to any one of <1> to <3>, wherein the fermenting bacteria further comprise a lactic acid bacteria starter. <6> The method for producing fermented milk according to <5>, wherein the lactic acid bacteria starter is a mixed culture of Streptococcus thermophilus and Lactobacillus bulgaricus.

[0035] <7> Fermented milk obtained by the method according to any one of the above items <1> to <6>. <8> Fermented milk obtained by the method according to any one of the above items <1> to <6>, wherein, when the storage period from the end of the day following the production date (day 0) is defined as one day, the fermented milk stored for 7 days has a pH of 4.0 or more and 4.7 or less at 10°C and a content of live Bifidobacterium bacteria of 3.5 x 10 per 100 g of fermented milk. ９ <9> Fermented milk obtained by the production method according to any one of <1> to <6>, wherein, when the storage period from the end of the day following the production date (day 0) is defined as one day, the fermented milk stored for 11 days has a pH of 4.0 or more and 4.7 or less at 10°C, and the content of live Bifidobacterium bacteria per 100 g of the fermented milk is 3.5 x 10 ９<10> Fermented milk obtained by the production method according to any one of <1> to <5>, wherein, when the storage period from the end of the day following the production date (day 0) is defined as one day, the fermented milk stored for 14 days has a pH of 4.0 or more and 4.7 or less at 10°C, and the content of live Bifidobacterium bacteria per 100 g of the fermented milk is 3.5 x 10 ９ <11> Fermented milk obtained by the production method according to any one of <1> to <6>, wherein, when the storage period from the end of the day following the production date (day 0) is defined as one day, the fermented milk stored for 21 days has a pH of 4.0 or more and 4.7 or less at 10°C, and the content of live Bifidobacterium bacteria per 100 g of the fermented milk is 3.5 x 10 ９ <12> Fermented milk obtained by the production method according to any one of <1> to <6>, wherein, when the storage period from the end of the day following the production date (day 0) is defined as one day, the fermented milk stored for 22 days has a pH of 4.0 or more and 4.7 or less at 10°C, and the content of live Bifidobacterium bacteria per 100 g of the fermented milk is 3.5 x 10 ９ <13> Fermented milk obtained by the production method according to any one of <1> to <6>, wherein, when the storage period from the end of the day following the production date (day 0) is defined as one day, the fermented milk stored for 23 days has a pH of 4.0 or more and 4.7 or less at 10°C, and the content of live Bifidobacterium bacteria per 100 g of the fermented milk is 3.5 x 10 ９ cfu or more, fermented milk.

[0036] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

[0037] <Measurement Method> The viable cell count of bifidobacteria was measured using TOS propionic acid agar medium (manufactured by Yakult Pharmaceutical Co., Ltd.). Specifically, the following procedure was performed: 1 g of sample (fermented product) was dissolved and suspended in 9 mL of 0.85% sterilized physiological saline, and the suspension was serially diluted and then anaerobically cultured in TOS medium (trans-oligosaccharide propionic acid agar medium, manufactured by Yakult Pharmaceutical Co., Ltd.) at 37°C for 72 hours, and the number of colonies was counted.

[0038] The iron content was measured by ICP (inductively coupled plasma) spectroscopy. The viable cell counts of "Lactococcus bacteria / Bifidobacteria" in the raw material composition were determined using the following method, and the ratio of the viable cell count of Lactococcus bacteria to the viable cell count of Bifidobacteria was calculated. <Lactococcus bacteria> 1 g of the raw material composition was dissolved and suspended in 9 mL of 0.85% sterilized saline, and the suspension was serially diluted. This diluted solution was aerobically cultured at 37°C for 72 hours using BCP-added plate count agar medium (manufactured by Eiken Chemical Co., Ltd.), and the number of colonies was counted. The viable cell count was calculated by multiplying the colony count by the dilution factor. <Bifidobacteria> 1 g of the raw material composition was dissolved and suspended in 9 mL of 0.85% sterilized saline, and the suspension was serially diluted. The diluted solution was anaerobically cultured at 37°C for 72 hours using TOS medium (trans-oligosaccharide propionic acid agar medium, manufactured by Yakult Pharmaceutical Co., Ltd.), and the number of colonies was counted. The number of colonies was multiplied by the dilution factor to determine the viable cell count.

[0039] <Ingredients Used> Skim milk powder: manufactured by Morinaga Milk Industry Co., Ltd., protein 34.0% by mass, fat 1.0% by mass, non-fat milk solids 95.2%, calcium content 1.1%. Granulated sugar: Mitsui Sugar Co., Ltd. product name "Granulated Sugar". Iron preparation (1): Taiyo Kagaku Co., Ltd. product name "Sunactive Fe-12A", preparation containing ferric pyrophosphate, iron content 12 mg / g. Iron preparation (2): San-Ei Gen F.F.I. Co., Ltd. product name "FE Base No. 36833", preparation containing ferric pyrophosphate, iron content 25 mg / g. Iron preparation (3): Mitsubishi Chemical Corporation product name "Sunferol", preparation containing sodium ferrous citrate, iron content 105 mg / g. Iron preparation (4): Showa Kako Co., Ltd. product name "ferrous ammonium citrate", a preparation containing ferrous ammonium citrate, iron content 171 mg / g. Bifidobacteria (1): Morinaga Milk Industry Co., Ltd., Bifidobacterium longum BB536 (NITE BP-02621 strain) bacterial culture. Bifidobacterium (2): Morinaga Milk Industry Co., Ltd., Bifidobacterium breve MCC1274 (FERM BP-11175 strain) bacterial culture. Lactococcus genus bacteria (1): Morinaga Milk Industry Co., Ltd., Lactococcus lactis (NITE BP-1204 strain) bacterial culture. Lactic acid bacteria starter (1): a commercially available mixed culture of Streptococcus thermophilus (S. thermophilus) and Lactobacillus bulgaricus (L. bulgaricus).

[0040] <Examples 1 to 27> Examples 1, 6 to 7, 9 to 10, 12 to 14, 16 to 23, and 25 to 27 are working examples, and Examples 2 to 4, 5, 8, 11, 15, and 24 are comparative examples.

[0041] Raw material compositions were prepared according to the formulations shown in Tables 1 to 5. Specifically, skim milk powder, granulated sugar, iron preparation, and room-temperature water (i.e., dissolution water) were mixed using a mixer and heated to 70°C for dissolution. The mixture was then homogenized using a homogenizer at 15 MPa, sterilized by heating at 90°C for 10 minutes, and cooled to 38°C. Bifidobacteria, Lactococcus bacteria, and a lactic acid bacteria starter were then added to obtain raw material compositions. In the raw material compositions, the "Lactococcus bacteria / Bifidobacteria" ratio, which represents the ratio of the live Lactococcus bacteria content (unit: cfu / 100g) to the live Bifidobacteria content (unit: cfu / 100g), was set to 0.4. The non-fat milk solids content of the raw material compositions was calculated from the non-fat milk solids content indicated on the raw material and the blending amounts of each raw material. Alternatively, it can be calculated by subtracting the fat content determined by the fat measurement method described above from the milk solids content. The milk solid content is calculated from the amount of milk solid content of the raw material, or by subtracting the solid content other than milk from the solid content. The raw material composition was then filled into a cup and kept at 38°C to ferment until the pH reached 4.7, and then cooled to 10°C to obtain fermented milk. The obtained fermented milk was stored in a refrigerator at 10°C for a predetermined period, and the number of bifidobacteria was measured using the method described above. The storage period was as shown in the table. For example, the day of production was considered to be day 0, and the day after production was considered to be day 1. In each example, the content of live bifidobacteria at the start of storage was 1 x 10 １０ cfu or more 5 x 10 １１ It was confirmed that the number of bifidobacteria was less than or equal to 4.7 cfu. The measurement results are shown in the tables and graphs in Figures 1 to 6. In Figures 1 to 6, the horizontal axis represents the storage period (unit: days) and the vertical axis represents the number of bifidobacteria (unit: cfu / 100 g). In each example, it was confirmed that the pH (measurement temperature: 10°C) was maintained within the range of 4.7 to 4.0 during the storage period shown in the tables.

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] As shown in the results in Table 1, the fermented food of Example 1 containing bifidobacteria, Lactococcus bacteria, and an iron-containing compound had a higher number of bifidobacteria after storage and improved viability compared to Examples 2 to 4, which did not contain either or both of Lactococcus bacteria and an iron-containing compound. In particular, comparing Examples 3 and 4, when Lactococcus bacteria were not contained, the number of bifidobacteria was significantly reduced after 11 days of storage in both Example 3, which contained an iron-containing compound, and Example 4, which did not contain an iron-containing compound. On the other hand, comparing Examples 1 and 2, when Lactococcus bacteria were contained, Example 1, which contained an iron-containing compound, had a significantly higher number of bifidobacteria after 18 days of storage compared to Example 2, which did not contain an iron-containing compound. These results suggest that the synergistic effect of Lactococcus bacteria and the iron-containing compound further improves the viability of bifidobacteria.

[0048] As shown in the results in Table 2, in all of Examples 5 to 7 using Bifidobacterium (1) and Examples 8 to 10 using Bifidobacterium (2), Examples 6, 7 and Examples 9, 10 containing Lactococcus bacteria and an iron-containing compound had a higher number of Bifidobacterium after storage and improved viability compared to Example 5 or Example 8 containing Lactococcus bacteria but not an iron-containing compound. Note that in all of Examples 6 and 7 using Bifidobacterium (1) and Examples 9 and 10 using Bifidobacterium (2), the higher the iron content, the higher the number of Bifidobacterium after storage and the improved viability.

[0049] As shown in the results in Table 3, compared to Example 11 which contained Lactococcus bacteria but no iron-containing compound, Example 12 which contained Lactococcus bacteria and an iron-containing compound, and the iron-containing compound was iron preparation (2), Example 13 which was iron preparation (3), and Example 14 which was iron preparation (4), all had a higher number of bifidobacteria after storage and improved survival.

[0050] As shown in the results in Table 4, compared to Example 15, which contained Lactococcus bacteria but no iron-containing compound, Examples 16 to 19, which contained Lactococcus bacteria and had an iron content of 0.3 to 5 mg / 100 g from iron preparation (2), and Examples 20 to 23, which contained iron content of 0.3 to 5 mg / 100 g from iron preparation (3), all had higher numbers of bifidobacteria after storage and improved viability. Note that in both Examples 16 to 19, which used iron preparation (2), and Examples 20 to 23, which used iron preparation (3), the higher the iron content, the higher the number of bifidobacteria after storage and the improved viability.

[0051] As shown in the results in Table 5, compared to Example 24 which contained Lactococcus bacteria but no iron-containing compound, Examples 25 to 27 which contained Lactococcus bacteria and an iron-containing compound and had an iron content of 0.9 to 10 mg / 100 g all had a higher number of bifidobacteria after storage and improved viability. Note that the higher the iron content, the higher the number of bifidobacteria after storage and the improved viability.

Claims

1. A fermented food comprising bifidobacteria, lactococci and iron-containing compounds.

2. The fermented food according to claim 1, wherein the iron content per 100 g of the fermented food is 0.3 mg or more.

3. The fermented food product of claim 1, wherein the iron-containing compound comprises non-heme iron.

4. The fermented food according to claim 3, wherein the iron-containing compound comprises one or more members selected from the group consisting of ferric pyrophosphate, ferrous citrate and ammonium ferric citrate.

5. The content of live bifidobacteria per 100 g of the fermented food is 1 x 10 ８ The fermented food according to claim 1, wherein the fermented food is 0.01 cfu or more.

6. The fermented food according to claim 1, wherein the bifidobacteria include one or more species selected from the group consisting of Bifidobacterium longum and Bifidobacterium breve.

7. The fermented food according to claim 1, wherein the Lactococcus bacteria includes Lactococcus lactis.

8. The fermented food product according to claim 1, wherein the fermented food product is fermented milk.

9. A method for producing a fermented food, comprising a step of fermenting a raw material composition containing bifidobacteria, lactococcus bacteria, and an iron-containing compound.

10. A method for improving the viability of bifidobacteria in a fermented product obtained by fermenting a raw material composition containing bifidobacteria, the method comprising fermenting a raw material composition containing bifidobacteria, Lactococcus bacteria, and an iron-containing compound.

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